North Korea said Monday it has successfully tested-fired a new mid-to-long-range ballistic missile that can carry a large nuclear warhead, claiming that the U.S. mainland is within its striking range.

North Korea said that a "large-size heavy nuclear warhead" can fit on its new ground-to-ground missile in its threat to launch a nuclear-tipped intercontinental ballistic missile (ICBM) capable of hitting the United States.

North Korean leader Kim Jong-un observed the launch of the rocket, called the Hwasong-12, on Sunday, according to the Korean Central News Agency (KCNA).

North Korea fired the missile from a site northwest of Pyongyang, according to South Korea's military. It marked the North's first provocation since South Korea's new President Moon Jae-in took office Wednesday.

The KCNA said that the missile reached a maximum altitude of 2,111.5 kilometers in an indication that it was a new type of intermediate-range ballistic missile (IRBM). It flew 787 km, it added.

"The test-fire aimed at verifying the tactical and technological specifications of the newly developed ballistic rocket capable of carrying a large-size heavy nuclear warhead," the report said in English.

Kim warned that the U.S. should not misjudge the reality that its mainland and operations in the Pacific region are in North Korea's "sighting range for a strike and that it has all-powerful means for a retaliatory strike," it added.

This set of photos carried by North Korea's main newspaper Rodong Sinmun on May 15, 2017, shows a new North Korean mid- and long-range ballistic missile, called the Hwasong-12, which was launched a day earlier. (For Use Only in the Republic of Korea. No Redistribution) (Yonhap)

If North Korea's claim is confirmed, the move marks a technical advance in its development of an ICBM.

North Korea's leader said in his New Year's message that the country has entered the final stage of preparing to launch an ICBM.

South Korea's military said more information is needed to verify the technical aspects of the missile, but it added that Pyongyang seems to have yet to master missile technology for "atmospheric reentry," a key element in developing an ICBM.

"The missile may have a maximum range capable of reaching Alaska and Hawaii if it is fired at a standard angle," said Kim Dong-yub, a professor at the Institute for Far Eastern Studies in Kyungnam University.

Photos released by the North's media showed that it looked like a missile unveiled at a military parade in April to mark the 105th birthday of late founder Kim Il-sung, experts said.

Footage aired by the state TV station showed that it was launched on what appeared to be a makeshift firing stand after being moved on a transport erector launcher (TEL), a move seen as aiming at avoiding damage due to possible failure.

North Korea launched a new IRBM, known as Pukguksong-2 in North Korea, from the same site on Feb. 12. The missile is known to be developed with the technology applied to submarine-launched ballistic missiles (SLBMs).

This composite photo (R) carried by North Korea's main newspaper Rodong Sinmun on May 15, 2017, shows a new North Korean mid-to-long-range ballistic missile called the Hwasong-12. The missile looks like the one unveiled at a military parade in April. (For Use Only in the Republic of Korea. No Redistribution) (Yonhap)

South Korea's unification ministry warned that North Korea should not miscalculate the situation.

"(The international community) has the shared view that North Korea's nuclear and missile provocations pose a grave threat to peace and security in the region and beyond the peninsula," Lee Duk-haeng, ministry spokesman, told a regular press briefing.

Lee declined to give the government's assessment of North Korea's intention, stating the need to take into account factors related to inter-Korean relations, including possible dialogue.

Experts said that the launch appeared aimed at testing South Korea's new president who has vowed to seek the dual-track approach of pushing for denuclearization and dialogue with Pyongyang.

Moon is widely expected to seek engagement with North Korea to improve long-strained ties, but Pyongyang's nuclear and missile programs are limiting his leeway for reconciliatory policies.

On Sunday, Moon said that his administration would deal resolutely with North Korea's provocations in a bid to ensure that Pyongyang would not "miscalculate" the situation.

Tensions heightened on the divided peninsula in recent weeks amid speculation that North Korea may conduct its sixth nuclear test.

Pyongyang appeared to refrain from conducting large-scale provocations, but the latest launch is likely to put Seoul and Washington's policy toward the North's regime to the test.

Choe Son-hui, a senior North Korean diplomat, said Saturday that Pyongyang would be willing to hold talks with Washington "under the right conditions."

The U.S. said it aims to pressure North Korea into dismantling its nuclear and missile programs through sanctions while remaining open to dialogue. U.S. President Donald Trump is pressing China to rein in its unruly neighbor.

"North Korea seems to seek dialogue with the U.S. on equal footing by strengthening its nuclear capabilities," said Kim Yong-hyun, a professor at Dongguk University. (Yonhap)

This set of photos carried by North Korea's main newspaper Rodong Sinmun on May 15, 2017, shows North Korean leader Kim Jong-un observing the test-fire of a new mid-to-long-range ballistic missile, called the Hwasong-12. (For Use Only in the Republic of Korea. No Redistribution) (Yonhap)